const user1 = { age: 11 }
const user2 = { age: 22 }
const user3 = { age: 33 }

const nameList = [ user1.age, user2.age, user3.age ]

function fn () {
    const num1 = 1
    const num2 = 2
}

fn()  //fn()执行完了fn()中的变量会被回收